#include<bits/stdc++.h>
using namespace std;
#define F first
#define S second
#define all(x) x.begin(),x.end()
#define pii pair<int,int>
#define pb push_back
#define sz(x) (int)(x.size())
#define chmin(x,y) x=min(x,y)
#define chmax(x,y) x=max(x,y)
#define vi vector<int>
#define vp vector<pii>
#define vvi vector<vi>
#define ykh mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count())
#define __lg(x) 63-__builtin_clzll(x)
#define pow2(x) (1LL<<x)
void __print(int x) {cerr << x;}
void __print(float x) {cerr << x;}
void __print(double x) {cerr << x;}
void __print(long double x) {cerr << x;}
void __print(char x) {cerr << '\'' << x << '\'';}
void __print(const char *x) {cerr << '\"' << x << '\"';}
void __print(const string &x) {cerr << '\"' << x << '\"';}
void __print(bool x) {cerr << (x ? "true" : "false");}
template<typename T, typename V>
void __print(const pair<T, V> &x) {cerr << '{'; __print(x.first); cerr << ','; __print(x.second); cerr << '}';}
template<typename T>
void __print(const T &x) {int f = 0; cerr << '{'; for (auto &i: x) cerr << (f++ ? "," : ""), __print(i); cerr << "}";}
void _print() {cerr << "]\n";}
template <typename T, typename... V>
void _print(T t, V... v) {__print(t); if (sizeof...(v)) cerr << ", "; _print(v...);}
void setIO(string s) {
freopen((s + ".in").c_str(), "r", stdin);
freopen((s + ".out").c_str(), "w", stdout);
}
#ifdef local
void CHECK();
void setio(){
freopen("/Users/iantsai/cpp/input.txt","r",stdin);
freopen("/Users/iantsai/cpp/output.txt","w",stdout);
}
#define debug(x...) cerr << "[" << #x << "] = ["; _print(x)
#else
void setio(){}
#define debug(x...)
#endif
#define TOI_is_so_de ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);setio();
const int mxn = 5e5 + 5;
bool vis[mxn], in[mxn];
vector<pii>adj[mxn];
vector<int>cur, ord;
vector<vector<int>>ans;
void dfs(int v){
while(sz(adj[v])){
auto [u, id] = adj[v].back();
adj[v].pop_back();
if(vis[id]) continue;
vis[id] = 1;
dfs(u);
}
ord.pb(v);
}
signed main(){
TOI_is_so_de;
int n, m;
cin >> n >> m;
for(int i = 1; i <= m; i++){
int v, u;
cin >> v >> u;
adj[v].pb({u, i});
adj[u].pb({v, i});
}
dfs(1);
ord.pop_back();
for(auto v : ord){
if(in[v] == 1){
vector<int> temp;
temp.pb(v);
while(cur.back() != v){
temp.pb(cur.back());
in[cur.back()] = 0;
cur.pop_back();
}
ans.pb(temp);
}
else{
in[v] = 1;
cur.pb(v);
continue;
}
}
ans.pb(cur);
for(auto i : ans){
for(auto v : i){
cout << v << ' ';
}
cout << '\n';
}
#ifdef local
CHECK();
#endif
}
/*
input:
*/
#ifdef local
void CHECK(){
cerr << "\n[Time]: " << 1000.0 * clock() / CLOCKS_PER_SEC << " ms.\n";
function<bool(string,string)> compareFiles = [](string p1, string p2)->bool {
std::ifstream file1(p1);
std::ifstream file2(p2);
if (!file1.is_open() || !file2.is_open())return false;
std::string line1, line2;
while (getline(file1, line1) && getline(file2, line2)) {
if (line1 != line2)return false;
}
int cnta=0,cntb=0;
while(getline(file1,line1))cnta++;
while(getline(file2,line2))cntb++;
return cntb-cnta<=1;
};
bool check = compareFiles("output.txt","expected.txt");
if (check) cerr<<"ACCEPTED\n";
else cerr<<"WRONG ANSWER!\n";
}
#else
#endif
